mm/gup_benchmark: handle gup failures

mstsirkin · torvalds · commit 09e35a4a1ca8 · 2018-04-13T17:10:27.000-07:00
Patch series "mm/get_user_pages_fast fixes, cleanups", v2. Turns out get_user_pages_fast and __get_user_pages_fast return different values on error when given a single page: __get_user_pages_fast returns 0. get_user_pages_fast returns either 0 or an error. Callers of get_user_pages_fast expect an error so fix it up to return an error consistently. Stress the difference between get_user_pages_fast and __get_user_pages_fast to make sure callers aren't confused. This patch (of 3): __gup_benchmark_ioctl does not handle the case where get_user_pages_fast fails: - a negative return code will cause a buffer overrun - returning with partial success will cause use of uninitialized memory. [akpm@linux-foundation.org: simplification] Link: http://lkml.kernel.org/r/1522962072-182137-3-git-send-email-mst@redhat.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Thorsten Leemhuis <regressions@leemhuis.info> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/gup_benchmark.c b/mm/gup_benchmark.c
@@ -23,7 +23,7 @@ static int __gup_benchmark_ioctl(unsigned int cmd,
 	struct page **pages;
 
 	nr_pages = gup->size / PAGE_SIZE;
-	pages = kvmalloc(sizeof(void *) * nr_pages, GFP_KERNEL);
+	pages = kvzalloc(sizeof(void *) * nr_pages, GFP_KERNEL);
 	if (!pages)
 		return -ENOMEM;
 
@@ -41,6 +41,8 @@ static int __gup_benchmark_ioctl(unsigned int cmd,
 		}
 
 		nr = get_user_pages_fast(addr, nr, gup->flags & 1, pages + i);
+		if (nr <= 0)
+			break;
 		i += nr;
 	}
 	end_time = ktime_get();

Original file line number	Diff line number	Diff line change
`@@ -23,7 +23,7 @@ static int __gup_benchmark_ioctl(unsigned int cmd,`
`23`	`23`	`struct page **pages;`
`24`	`24`
`25`	`25`	`nr_pages = gup->size / PAGE_SIZE;`
`26`		`- pages = kvmalloc(sizeof(void ) nr_pages, GFP_KERNEL);`
	`26`	`+ pages = kvzalloc(sizeof(void ) nr_pages, GFP_KERNEL);`
`27`	`27`	`if (!pages)`
`28`	`28`	`return -ENOMEM;`
`29`	`29`
`@@ -41,6 +41,8 @@ static int __gup_benchmark_ioctl(unsigned int cmd,`
`41`	`41`	`}`
`42`	`42`
`43`	`43`	`nr = get_user_pages_fast(addr, nr, gup->flags & 1, pages + i);`
	`44`	`+ if (nr <= 0)`
	`45`	`+ break;`
`44`	`46`	`i += nr;`
`45`	`47`	`}`
`46`	`48`	`end_time = ktime_get();`